This invention relates to a machine with an inside space (working chamber) which periodically changes its volume and more particularly refers to a machine that is mainly used as a power engine, as pump for liquids and gases or as a compressor for gases.
Such machines commonly use for their operation the stroke movement of a cylindrical piston in a cylindrical hole. The linear motion of the piston is converted to the rotating motion needed for most purpose with a mechanism consisting of a connecting rod and crankshaft. The motion of additional parts (valves) is needed to open and close the working chamber for the inlet and outlet of the operating fluid. A separate mechanism is required for this purpose.
The advantage of such constructions is mainly that the cylindrical working chamber can be sealed easily and efficiently. Furthermore these machines have been built for decades and reached a high degree of sophistication through a process of continual improvement.
Their most notable disadvantages are:
1. The mechanism for the motion of the valves impedes (on account of its inertia) the quick inlet and outlet of the working medium and moreover is complicated, expensive and delicate.
2. The time-law for the change of the volume in the working chamber is not the best one either for diminishing the accelerating forces, nor for increasing the efficiency of the machine, but it cannot be changed since it is imposed on account of the kinetic principle of the crankshaft.
3. During the conversion of the linear movement to the rotational movement strong oblique forces appear on the piston that cause great friction losses and wear.
4. The length of the stroke of the piston remains constant and subsequently the power of the engine, at constant rotational speed. Therefore a supplementary gear box is needed for most applications.
Numerous attempts to escape from these disadvantages have been undertaken and are being continuously carried out, but they are confronted with other difficulties like problems of construction, sealing and wear; or they cause reduction of efficiency.